While Brazilian horseman Álvaro Affonso de Miranda Neto is competing in the Olympics next week as a show jumping rider, his spurned spouse, Athina Onassis, is going for the gold herself — playing to win their divorce battle by hiring Manhattan celebrity attorney Robert Cohen.

The high-profile lawyer — known for his aggressive representation of celebrities such as Ivana Trump and Chris Rock in their divorces — was spotted boarding a plane earlier this week en route to Belgium, where Onassis lives, reports The Post’s Julia Marsh.

Athina, pictured with Álvaro (above), is the last surviving relative of Greek shipping magnate Aristotle Onassis. A source further told Marsh that the divorce is heating up with Onassis, 31, now living apart from Neto, 43. Cohen was hired to oversee legal strategy, the source said.

Onassis will skip her soon-to-be ex’s individual and team jumping events scheduled for Sunday, the source said.

A member of the heiress’ private security team caught Neto, known as “Doda,” in bed with a blonde at their $2 million Florida home recently, according to reports.

Onassis — who was Jackie Kennedy’s step-granddaughter — inherited half of her grandfather’s $5 billion fortune. When she received the dough she was only 18, making her the world’s richest teenager at the time.

Meanwhile, the heiress’ short life has been long on tragedy: Her mother died when she was just 3 years old, and she battled with her father, Thierry Roussel, for years over her fortune.

Neto, who has a daughter with late Brazillian model Cibele Dorsa, is a four-time Olympic rider and two-time bronze medalist (at the 1996 and 2000 games). He and Onassis own AD Sport Horses, which breeds and trains horses.